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Designing the photonic environment yields a mechanism for creating bound states in the continuum over a wide range of angles.

Topological materials have been at the forefront of research across various fields of physics in hopes of harnessing properties such as scatter-free transport due to protection from defects and disorder. Photonic systems are ideal test beds for topological models and seek to profit from the idea of topological robustness for applications. Recent progress in 3D-printing of microscopic structures has allowed for a range of implementations of topological systems. We review recent work on topological models realized particularly in photonic crystals and waveguide arrays fabricated by 3D micro-printing. The opportunities that this technique provides are a result of its facility to tune the refractive index, compatibility with infiltration methods, and its ability to fabricate a wide range of flexible geometries.

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Weyl points are point degeneracies that occur in momentum space of 3D periodic materials and are associated with a quantized topological charge. Here, the splitting of a quadratic (charge‐2) Weyl point into two linear (charge‐1) Weyl points in a 3D micro‐printed photonic crystal is observed experimentally via Fourier‐transform infrared spectroscopy. Using a theoretical analysis rooted in symmetry arguments, it is shown that this splitting occurs along high‐symmetry directions in the Brillouin zone. This micro‐scale observation and control of Weyl points is important for realizing robust topological devices in the near‐infrared.